Transition Elements and Ligands Flashcards
What are the electron configurations for Chromium and Copper?
- Cr - 1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1
- Cu - 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1
Why are the electron configurations for copper and chromium different?
Half-filled 3d and 4s sub-shells are more stable than partially filled
Physical properties of transition metals? (3)
- High MP and BP
- Conducts heat and electricity
- Used for construction, cables, pipes etc.
Properties of transition metal compounds? (3)
- Form coloured compounds
- Act as catalysts (due to variable oxidation states)
- Same element can have different oxidation state depending on the compound
What are the oxidation states and colours for Titanium? (1)
+3 = lilac
What are the oxidation states and colours of Vanadium? (4)
\+2 = lilac \+3 = green \+4 = blue \+5 = yellow
What are the oxidation states and colours of Chromium? (3)
\+2 = blue \+3 = green \+6 = orange
What are the oxidation states and colours for Manganese? (4)
\+2 = pale pink \+4 = brown \+6 = green \+7 = violet
What are the oxidation states and colours for Iron? (2)
\+2 = pale green \+3 = pale yellow
Wha are the oxidation states and colours for cobalt? (2)
\+2 = pink \+3 = green
What are the oxidation states and colours of Nickel? (1)
+2 = green
What are the colours and oxidation states of copper? (1)
+3 = blue
What are catalysts?
Substances that provide an alternate pathway with a lower activation energy
Why are transition metals good catalysts? (2)
- Transfer electrons easily
- Provide a site to react - reactants can be held in place by adsorption and are released by desorption
What are some examples of reactions where a transition metal acts as a heterogeneous catalyst? (4)
- Haber process - Fe2+ catalyst
- Contact process - V2O5 catalyst
- Hydrogenation of alkenes - Ni
- Decomposition of hydrogen peroxide - MnO2-
What is an example of a reaction where a transition element acts a homogeneous catalyst?
Fe 2+ catalyses the reaction between iodide and peroxidisulphate, S2O8 2-
What is the definition of a complex ion?
Transition metal ion bonded to one or more ligands by a coordinate bond
What is the definition of a ligand?
A molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond
What is the definition of a coordinate bond?
When one of the bonded atoms provides both electrons to the bond. Also known as a dative covalent bond
What is meant by coordination number?
Number of coordinate bonds attached to the central metal ion
What is meant by a mono-dentate ligand?
A ligand that forms 1 coordinate bond per ligand with the central metal ion
What are some examples of mono-dentate ligands? (6)
- H2O:
- :NH3
- :SCN (-1)
- :CN (-1)
- :Cl (-1)
- :OH (-1)
What is meant by a bi-dentate ligand?
Donates 2 pairs of electrons and forms 2 coordinate bonds with the central metal ion
What are some examples of bi-dentate ligands? (3)
- Ethane-1,2-diamine -> :NH2 - CH2 - CH2 - :NH2 (no overall charge)
- Ethandioate -> :O - C(=O) - C(=O) - O: (-2 charge)
- Ketones (no overall charge)
What is meant by a multi-dentate ligand? Example?
A ligand that donates 3 or more electron pairs and forms 3 or more coordinate bonds
e.g. EDTA (6 coordinate bonds)
What is EDTA used for? (5)
- Bind to metals to lower conc.
- Used in detergents to soften water
- Bind to metal in food to slow oxidation
- Added to blood to prevent clotting
- Treat mercury poisoning
What shape do 6 coordinate no. complex ions form?
Octahedreal
What shape does a 4 coordinate no. complex ion form? What are the exceptions?
- Tetrahedral
- Pt 2+, Pd 2+ and Au 3+ are exceptions - form square planar
What are the conditions for an optical isomer? How would you draw one? (3)
- Coordination no. of 6
- Octahedral
- With 2 or more bi-dentate ligands
How are complex ions used in medicine? (5)
- Cis Platin [PtCl2(NH3)2] was a drug used for cancer
- Binds to DNA of fast growing cancer cell - prevents from replicating
- Cells own repair system leads to death of cells
- Basis for chemotherapy and has side effects
- Newer treatments involve carboplatin as it has fewer side effects and lower doses can be used
What is a ligand substitution reaction?
When one ligand in a complex ion is replaced with another
Why do some ligands get displaced?
Other ligands have a combine more strongly with the transition metal
What is the colour change and equation for the reaction of Cu 2+ with OH-?
Cu 2+ (aq) + 2OH- (aq) -> Cu(OH)2 (s)
Pale blue solution -> light blue ppt.
